1. Field of the Invention
This invention is related to beacons that are used to guide rescuers to individuals who are lost, buried, or trapped. Specifically, it relates to the use of sonic (sound generating) rescue beacons, designed to guide rescuers to individuals who are trapped in a structure such as a home or office building which has collapsed as a result of a natural disaster, an accident, or an intentional act of sabotage.
2. Description of the Related Art
When people are trapped under collapsed structures, rescuers often arrive with a variety of “aids” including specially trained dogs, thermal imaging cameras, search robots, specialized listening devices, flexible fiber optic cameras, pole-mounted and robotic search cameras, Infrared thermal imaging, microwaves to detect breathing or motion, carbon dioxide detection, and radio receiving devices sensitive to transmissions from cell phones or walkie-talkies which are sometimes in the possession of victims. However none of the aforementioned methods is consistently successful in these difficult circumstances and, every year, many thousands of individuals perish in collapsed structures from earthquakes, tornadoes and the like. The first 24 hours, following a disaster are the most critical. For example, after an earthquake, 90% of the survivors are saved in that period by rescuers using simple tools. It takes time for specialized rescue teams to arrive. By that time, many lives are lost. Therefore, there exists a need for a way to amplify the effectiveness of trapped survivors who are trying to bring their plight to the attention of first responders during the critical first day and, as well, to amplify the effectiveness of rescuers in locating survivors in that time period.
One way to achieve this “amplification” of effort is with rescue beacons of various kinds which are in proximity to the victims. A number of devices use the electromagnetic spectrum (radio waves) for this purpose. For example, U.S. Pat. No. 5,193,215, issued on Mar. 9, 1993, to Anthony L Olmer, describes a radio device which can transmit a distress signal and give precise local coordinates in the transmission. U.S. Pat. No. 5,995,982, issued on Sep. 21, 1999 to Marc Jean Moulin, describes a simple radio location device intended to aid in the rescue of victims of avalanches. Devices like Moulin's, rely on the notion that rescuers with equipment to sense “field strength” will succeed in localizing a radio emission source.
These, and other, radio devices can lead searchers to a general location over vast distances. But, since structural collapses rarely go unnoticed—especially where they are associated with disasters such as earthquakes, landslides, tornadoes, and so on—radio location is rarely needed. In such disasters, the challenge is to know where within the field of rubble to focus the effort to recover survivors. In such circumstances, radio beacons may be attenuated so severely by the overlying rubble that they can no longer be detected and the distribution pattern which, because of the characteristics of antennas, is often very irregular anyway, may become even more so, frustrating the efforts of rescuers.
There are, of course, more sophisticated radio location techniques. For examples, U.S. Pat. No. 6,031,482, issued on Feb. 29, 2000 to Lemaitre, et al, describes a technique using multiple antennas to detect an electromagnetic signature of movement from a victim buried in an avalanche. This system is designed, specifically, for snow rescue and its efficacy in a field of rubble is not described. In any case, first responders are unlikely to be equipped with advanced radio location equipment which may take hours or even days to arrive. Victims who may be seriously injured require assistance as soon as possible.